tbuckley/cabot-search huggingface dataset:
Abstract P2077: FoxO3 Transcription Factor Regulates Myocyte Contractility And Calcium Homeostasis In Diabetic Cardiomyopathy
Authors: Gourav Bhardwaj, Christie Penniman, Satya Murthy Tadinada, Qian Shi, Biyi Chen, Colette Nowers, Eric T Weatherford, Evan dale Abel, Long-Sheng Song, Brian O'Neill
Journal: Circulation Research (2023)

Diabetes is a risk factor for heart failure with preserved ejection fractions (HFpEF). Calcium (Ca 2+ ) mishandling and diastolic abnormalities are the characteristics of diabetic cardiomyopathy (DCM), but the molecular mechanisms of these are elusive. FoxO transcription factors (FoxOs) are suppressed by insulin and this study evaluated the role of FoxO3 in myocardial contractility and Ca 2+ handling in the heart of a mouse model of type 1 diabetes. We show that cardiomyocyte-restricted deletion of FoxO3 (H-FoxO3 KO) prevented reduction in the peak rate of left ventricular (LV) pressure (dP/dt max) and prevented the increase in the minimum rate of fall in LV pressure (dP/dt min) that was evident after 4-7 weeks of Streptozotocin (STZ) diabetes. Time for pressure decay of LV while relaxation (Tau) was partially increased in STZ hearts and tended to decrease in STZ H-FoxO3 KO. Echocardiography showed LVEF was unchanged in control and H-FoxO3 KO animals treated with/without STZ. Ca 2+ imaging in perfused hearts found that Ca 2+ transient amplitude was decreased and decay kinetics prolonged (indicates decreased SERCA activity) in STZ hearts, but these changes were prevented in STZ H-FoxO3 KO. Phosphorylation of SERCA at Thr484 by SPEG (Striated muscle preferentially expressed protein kinase) controls Ca 2+ re-uptake and cardiac contractility. We show that STZ diabetes decreases SPEG protein and pSERCA2a Thr484 , but levels of each were normalized or increased in STZ H-FoxO3 KO. Mechanistically, overexpression of FoxO3 in neonatal cardiomyocytes increases high-molecular weight SPEG adducts when proteasome degradation was inhibited with MG-132, suggesting that ubiquitin-mediated degradation of SPEG is a mechanism by which FoxO3 controls Ca 2+ handling via SERCA phosphorylation. SERCA function requires ATP, thus, we evaluated mitochondrial energetics in these animals. Respiratory capacity in saponin-permeabilized cardiac fibers was unchanged in hearts from controls and H-FoxO3 KO treated with/without STZ. ATP generation was decreased in STZ hearts but was not normalized in STZ-H FoxO3 KO. These data indicate FoxO3 regulates myocyte contractility via SPEG degradation to control intracellular Ca 2+ via pSERCA2a Thr484 in the heart in a type 1 diabetes model.
Abstract P3066: TSC2-mTOR Axis Exerts Biased Control Over Macrophage Infiltration Following Myocardial Infarction
Authors: Mohammad Keykhaei, Navid Koleini, Mariam Meddeb, Mark J Ranek, Farnaz Farshidfar, Edwin Yoo, Abigail Mulligan, David A Kass
Journal: Circulation Research (2023)

Introduction: The mechanistic target of rapamycin complex 1 (mTORC1) is an evolutionarily conserved serine/threonine kinase, which regulates pivotal physiological processes. mTORC1 activity is tightly regulated upstream by the tuberous sclerosis complex (TSC) which consists of TSC1 and TSC2. In macrophages as throughout the immune system, mTORC1 is a potent regulator of cell activation and function. Myocardial infarction (MI) is associated with stimulation of mTORC1; however, studies vary as to whether this activation is beneficial or detrimental, and its influence on macrophage differentiation, and infiltration after MI is unknown. Hypothesis: We tested the hypothesis that cardiac infiltration of macrophages following MI is regulated by their expression of TSC2. Methods/Results: Macrophage-specific TSC2 knock-out mice (TSC2-LyzM) were made by crossing mice with floxed-TSC2 and LysM-Cre that display a significant reduction of macrophage TSC2 protein. TSC2-LyzM bone marrow-derived macrophages (BMDMs) have constitutive mTORC1 activation reflected by phosphorylation of downstream targets S6K1 and 4E-BP1 and were correspondingly larger. To assess macrophage polarization, cells were stimulated with LPS to promote an M1-like phenotype or IL-4 to induce an M2-like phenotype. LPS- treated TSC2-LyzM BMDMs secreted more of the proinflammatory cytokine TNF-a, while IL-4 stimulation resulted in less of an M2 program, with significantly less Arg1, Mrc1, and Rentla expression. These findings show TSC2 is required for normal BMDM polarization. We next tested if TSC2 impacts macrophage myocardial infiltration after MI. Macrophages were identified as CD45+CD11b+CD64+ and further parsed by CCR2 and MHC-II. In concordance with prior studies, we found substantial infiltration of CCR2+ (BMDMs) macrophages in both genotype groups after MI. However, more TSC2-LyzM had increased CCR2+ MHC-II+ phenotype (infiltrating macrophages) versus wild-type. Conclusion: Overall, our findings highlight a key role for the TSC2-mTORC1 pathway in regulating macrophage fate specification and cardiac infiltration following a MI. This supports novel signaling control over BMDMs by TSC2-phosphorylation mediated mTORC1 activation or inhibition.
Abstract P1171: Golgi Localized DHHC3 And DHHC7 Contribute To The Initiation Of The Cardiac Hypertrophy Response In Vivo
Authors: Tanya A Baldwin, Matthew J Brody, Yasuhide Kuwabara, Weiqi Zhang, Jeffery D Molkentin
Journal: Circulation Research (2023)

Lipid modifications provide a layer of control over cardiac signaling molecules, including small GTPases and heterotrimeric G-proteins. Lipidation of signaling factors often permits their preferential localization to intracellular membranes and organelles where they then activate downstream effectors. S-palmitoylation is a reversible lipid modification catalyzed by a family of 23 palmitoyl acyltransferases, which are characterized by a conserved zinc finger-like aspartate-histidine-histidine-cystine (zDHHC) domain. Although the importance of GTPase palmitoylation is appreciated, our understanding of enzyme-substrate specificity remains uncertain and how these enzymes regulate cardiac stress signaling and hypertrophy is unknown. To examine the roles of the cardiac-expressed zDHHCs, we overexpressed zDHHC3, 5, 6, 7 and 13 using adeno-associated viruses. Overexpression of membrane-localized zDHHC5, ER localized zDHHC6 or Golgi-localized zDHHC13 had no effect on cardiac function, while overexpression of zDHHC3 or zDHHC7 (both Golgi-localized) caused dilated hypertrophic cardiomyopathy. zDHHC3 and zDHHC7 expression were also upregulated in the heart in response to transverse aortic constriction. To gain a better understanding of the physiological role of zDHHC3 and zDHHC7 in the heart we utilized gene-deleted mice subjected to models of pathological hypertrophy. At baseline, neither single (zDHHC3 and zDHHC7) or double (zDHHC3/7) knockout mice exhibit alterations in cardiac function. Total levels of GTPase signaling proteins are unchanged, although both single and double knockout mice have reduced palmitoylation of Gαs and Rac1. In response to pressure overload, knockout of both zDHHC3/7 delayed hypertrophic progression at an early timepoint (1 week), although the response is unchanged at a late timepoint (8 weeks). We conclude that both zDHHC3 and 7 contribute to the initiation of cardiac hypertrophy but are not key regulators of hypertrophic signaling.
Abstract P2194: Investigating The Role Of Angiotensin II In The Pathogenesis Of Atrial Fibrillation In Covid-19 Patients Through Blocking The Renin-Angiotensin-Aldosterone System
Authors: Angela Khidhir, Thomas Drago, Usman Najam, Sourabh Goyal, Michael Beshara, Leonard Palatnic, Brian Chatterton
Journal: Circulation Research (2023)

Background: COVID-19 was found to be associated with a greater risk of developing atrial fibrillation (AF). It is thought that COVID-19 enters cells using its surface spike protein, which binds to the ACE-2 receptor and downregulates it. One of the functions of ACE-2 is converting the pro-inflammatory, anti-fibrinolytic angiotensin II (Ang II) to angiotensin I (Ang I). Therefore, when ACE-2 is downregulated, more Ang II is available to trigger its downstream detrimental effects. Thus, we hypothesized that blocking the effects of Ang II using ACE inhibitors (ACEis) or ARBs would confer a protective effect against the risk of AF. Objective: The purpose of this project was to conduct a retrospective cohort study to determine whether treatment with an ACEi/ARB would prevent the development of AF in patients hospitalized for COVID-19. This would help us better understand the pathogenesis of AF in COVID-19 patients. It would also help us decide whether prophylactic treatment with ACEi/ARB would help reduce the risk. Methods: We reviewed the records of all patients admitted for at least seven days for COVID-19 between January 2021 and June 2021. Of 5430 charts, 188 met the inclusion criteria. Results: Approximately 4.8% of patients hospitalized for COVID-19 developed AF. About 6.74% of patients that were not on an ACEi/ARB at any point during their hospitalization developed AF, whereas none of the patients on an ACEi/ARB developed AF, making the relative risk (RR) 0.1871 (95% CI 0.0108 to 3.2377, p-value 0.2492), and the number needed to treat 14.8. Interestingly, in the patients with a previous diagnosis of AF, there was also no statistically significant difference in the need to escalate rate or rhythm control strategy between patients on an ACEi/ARB compared to those who were not (6.67% vs 14.29%, respectively), with a RR of 0.4667 (95% CI: 0.0546 - 4.0629, p-value 0.4900). Conclusion: Our data to date show that the use of an ACEi/ARB is not associated with a statistically significant decrease in the risk of AF in patients hospitalized with COVID-19, which suggests that there may be another cellular mechanism by which COVID-19 causes AF. Therefore, prophylactically treating patients with an ACEi/ARB or holding them on admission may have no influence on the risk of AF.
Abstract P1023: Nonsense Mutations In Atrial Myofilament Regulatory Protein MyBP-HL Are Subject To Proteolytic Degradation And Loss Of Functional Protein
Authors: Alejandro A Alvarez-Arce, Lucas Wittenkeller, Hope Burnham, David Y Barefield
Journal: Circulation Research (2023)

Background: Myosin binding protein-H like (MyBP-HL) is a recently identified atrial myofilament protein encoded by the gene MYBPHL. The Arg255Stop mutant has been linked to atrial enlargement, atrial fibrillation, and dilated cardiomyopathy. Deletion of MYBPHL in mice recapitulates this human phenotype. MyBP-HL is composed of two Immunoglobulin domains (Ig) and one Fibronectin domain (FnIII), like the structure and sequence of the last three C-terminal domains (C8-C9-C10) of cardiac myosin binding protein-C (cMyBP-C). cMyBP-C nonsense mutations fail in myofilament incorporation and result in a rapid degradation of the truncated protein and are a major cause of hypertrophic cardiomyopathy. There are 9 premature stop mutations in MYBPHL identified in humans (Gln29, Trp54, Arg113, Tyr123, Trp158, Trp192, Lys250, Arg255, and Tyr307). Hypothesis: We hypothesize that MYBPHL nonsense mutations will share a common mechanism that leads to MyBP-HL failing to integrate into the sarcomere, resulting in truncated MyBP-HL degradation and loss myofilament incorporation. Results: We demonstrate heterologous expression of MyBP-HL in neonatal rat cardiomyocytes can incorporate in a similar sarcomere pattern as cMyBP-C. Expression of the nine nonsense mutations do not localize into the sarcomere. Neonatal rat cardiomyocytes transfected with MyBP-HL constructs were treated with proteasome and/or calpain inhibitors. We observed that wild-type MyBP-HL and MyBP-HL truncating mutations are degraded mainly by the proteasome, although we also identified a significant calpain involvement in MyBP-HL degradation. Shorter MyBP-HL truncated peptides are degraded as a poisoning peptides, but longer peptides are not degraded. Conclusion: Based on these data, we demonstrated that MYBPHL nonsense mutations prevent MyBP-HL incorporation into the thick filament as are subject to degradation. The differential expression of short vs. long truncating MyBP-HL mutants suggest a differential pathogenic mechanism for subsets of these mutations.
Abstract GS.102: Cd206 <sup>+</sup> Il-4rα <sup>+</sup> Macrophages Are Drivers Of Adverse Cardiac Remodeling In Ischemic Cardiomyopathy
Authors: Qiongxin Wang, Ameen Ismahil, Gregg Rokosh, Tariq Hamid, Guihua Zhou, Yujie Zhu, Steven M Pogwizd, Sumanth D Prabhu
Journal: Circulation Research (2023)

Background: Cardiac macrophages are significantly expanded in chronic heart failure (HF); however, their role is unclear. We tested the hypothesis that CD206 + macrophages expressing interleukin (IL)-4Rα in the failing heart are key drivers of adverse left ventricular (LV) remodeling and ischemic cardiomyopathy. Methods and Results: Adult male C57BL/6 (WT) mice underwent non-reperfused myocardial infarction (MI) to induce HF, or sham operation, and cardiac macrophages were profiled using flow cytometry. As compared to sham hearts, both the frequency and absolute number of CD206 + macrophages steadily increased in post-MI hearts during the progression of LV remodeling and HF, such that at 8 w post-MI they comprised ~85% of macrophages. These macrophages were exclusively proliferative and predominantly C-C motif chemokine receptor (CCR2) - with nearly half expressing IL-4Rα, and correlated with LV dysfunction and fibrosis. IL-4-polarized bone marrow derived CD206 + macrophages exhibited marked upregulation of found in inflammatory zone (FIZZ)1 and induced FIZZ1-dependent myofibroblast differentiation of cardiac mesenchymal stem cells (cMSCs), in part related to DLL-4/Jagged1-Notch1 signaling. Intramyocardial adoptive transfer of M[IL-4], but not M[IL-10], macrophages induced progressive LV dilation and dysfunction and augmented cardiac fibrosis over 4 weeks in naïve mice. In vivo IL-4Rα gene silencing in mice with established HF effectively depleted cardiac CD206 + IL-4Rα + macrophages and induced reverse LV remodeling, improving fibrosis, neovascularization, and dysfunction, and suppressing local and systemic inflammation. Lastly, alternatively activated CD206 + and CD163 + macrophages were significantly expanded in human failing hearts and correlated with cardiac fibrosis, with the majority of CD163 + macrophages expressing IL-4Rα and FIZZ3, the human homolog of FIZZ1. Conclusion: CD206 + IL-4Rα + macrophages proliferate and expand in the failing heart and are key mediators of pathological remodeling and fibrosis, in part through the secretion of FIZZ1. Inhibition of CD206 + macrophage IL-4Rα signaling may be a fruitful therapeutic approach for alleviating LV remodeling in HF.
Abstract P2149: Modulation Of Cardiac Fibrosis By SGLT-2 Inhibitor Canagliflozin And DPP-4 Inhibitor Sitagliptin In A Swine Model For Chronic Myocardial Ischemia: A Comparative Analysis
Authors: Dwight D Harris, Sharif A Sabe, Mark Broadwin, Mohamed Sabra, Cynthia Xu, Ruhul Abid, Frank W Sellke
Journal: Circulation Research (2023)

Objective: Clinical data suggests cardiovascular benefits from anti-diabetes drugs including SGLT-2 and DPP-4 inhibitors, but the mechanisms remain unclear. This study evaluates the effect of DPP-4 inhibitor sitagliptin and SGLT-2 inhibitor canagliflozin on myocardial fibrosis in a swine model for chronic myocardial ischemia. Methods: Twenty-one Yorkshire swine underwent ameroid constrictor placement on the left coronary circumflex to model chronic myocardial ischemia. Two weeks post-op, swine were assigned to one of three groups: control (CON, n=8), canagliflozin 300mg daily (CAN, n=8), or Sitagliptin 100mg daily (SIT, n=5). After 5 weeks of treatment, swine underwent terminal harvest and tissue collection. Fibrosis was quantified using Masson's trichrome. Immunoblotting was used to quantify protein expression. Results: Trichrome stain showed a significant decrease in perivascular and interstitial fibrosis in the CAN and SIT groups compared to CON (all p&lt;0.05) but no difference between the SIT and CAN groups (Figure 1). Immunoblot showed a decrease in Jak2, pSTAT3 to STAT 3 Ratio, pSMAD 2/3, and SMAD 2/3 (all p&lt;0.05) in the SIT group compared to CON, and decreased pSTAT3 to STAT 3 Ratio, pSMAD 2/3, and SMAD 2/3 (all p&lt;0.05) in the CAN group compared to CON. Jak2 was decreased in the SIT compared to CAN group (p=0.04), and MMP-13 was decreased in the CAN compared to SIT group (p&lt;0.001). Conclusions: Sitagliptin and canagliflozin result in a similar reduction in perivascular and interstitial fibrosis in a swine model for chronic myocardial ischemia. This reduction in fibrosis likely contributes to the improved cardiovascular outcomes seen with DPP-4 and SGLT-2 inhibitors.
Abstract P2125: Melatonin As A Strategy To Mitigate Late Doxorubicin-induced Cardiotoxicity
Authors: Marisol Fernandez Ortiz, Logan Davis, David Gius, Gregory Aune
Journal: Circulation Research (2023)

There are more than 500,000 childhood cancer survivors in the USA. These patients have an elevated risk of developing life-threatening health problems, cardiovascular disease being the main cause of early mortality in this population. Most of these survivors received anthracyclines. These antitumor agents are the benchmark for treatment in pediatric and adult oncology. Doxorubicin (DOX) is the most used anthracycline due to its high efficacy against solid cancer and hematological malignancies. With the improvements in five-year survival rates and growing survivor population, the long-term wellbeing of these cancer survivors is a primary healthcare concern.The clinical utility of DOX is compromised by its link to cardiac disease development after a long asymptomatic period preceding cardiac dysfunction and irreversible heart failure. A mechanism proposed for this late DOX - i nduced c ardiotoxicity ( DOXIC ) is the accumulation of DOX in cardiac fibroblasts (CFs), a key cell type in cardiac maturation and injury response, which increases mitochondrial oxidative stress, declining heart function over decades. The use of a safe approach against DOXIC without impeding the antitumor activity of DOX is a major clinical challenge.Our study proposes melatonin (aMT) as a strategy against late DOXIC. This mitochondria-targeted antioxidant has been reported to enhance the efficacy of chemotherapy and has been used safely in patients even at high doses. Our in vitro results showed that young primary murine CFs presented higher proliferation and fewer dead cells with continuous exposure to aMT post-DOX treatment (% of death at 24h: 100% in DOX 3uM 3h, 86% DOX + 5uM aMT, 7% DOX + 10uM aMT, 0% DOX + 20uM aMT). Our i n vivo results proved that aMT protected against early DOXIC in young mice, with a fractional shortening (FS) similar to vehicle. Furthermore, aMT was used as a rescue strategy in mature mice with impaired cardiac function. This aMT intervention recovered FS from 28 to 39%, suggesting aMT could counteract late DOXIC. These experiments produce the first data of this kind using aMT as a preventive and rescue strategy to mitigate late DOXIC with an approach that is closely aligned with the cardiac outcomes noted in childhood cancer survivors decades after DOX exposure.
Abstract P2096: Characterization Of Unique Dystrophin Isoforms In Epicardial Cells
Authors: Sarah Ware, Terry Gemelli, Beverly A Rothermel, Dan Tong, Pradeep P Mammen
Journal: Circulation Research (2023)

Duchenne muscular dystrophy (DMD) is caused by mutations that abolish dystrophin expression. Dilated cardiomyopathy, the leading cause of death in DMD patients, is characterized by the development of severe subepicardial fibrosis that precedes cardiac dysfunction. While the cellular mechanisms governing this process remain unknown, a recent study in mdx/mTR mice suggested that inflammation, in response to cardiomyocyte damage caused by dystrophin deficiency, activates the epicardium to undergo epithelial-to-mesenchymal transition into fibroblasts, thereby contributing to subepicardial fibrosis. Whether dystrophin plays an epicardial-autonomous role in this process has not been investigated. The DMD gene produces at least eight dystrophin isoforms from seven independent, tissue-specific promoters ( Fig. 1 ). We used an immortalized mouse embryonic epicardial cell line to determine which isoforms are present. We found transcripts for the full-length muscle isoform of dystrophin (Dp427m) in addition to the ubiquitous, more abundant Dp71 and Dp40 isoforms. RT-PCR and western blot analysis revealed the presence of three different Dp71 splice variants. Immunofluorescence and subcellular fractionation determined that Dp71 localizes primarily to the nucleus. Studies are ongoing to understand the role of Dp71 in epicardial cell proliferation and gene expression, as well as defining changes in dystrophin expression during the transition from the activated epicardium to myofibroblasts. Further investigation is needed to determine the role of these shorter isoforms in DMD pathology and how gene editing of full-length dystrophin may impact their function.
Abstract P3141: Age-associated Alterations In Sialylation Affect Nav1.5 Channel Function And Contribute To Cardiac Dysfunction
Authors: Adriana Tarantino, Simona Coviello, Andrea Ghiroldi, Dario Melgari, Anthony Frosio, Serena Calamaio, Marco Piccoli, Giuseppe Ciconte, Carlo Pappone, Luigi Anastasia
Journal: Circulation Research (2023)

Voltage-gated sodium channel Nav1.5 plays a pivotal role in the proper functioning of cardiac muscle cells by mediating their depolarization. Sialylation, a post-translational modification involving the addition of negatively charged sialic acid moieties, is essential for Nav1.5 functionality. Altered sialylation has been observed in various cardiovascular diseases, including Chagas disease, and congenital disorders of glycosylation affecting the heart. Furthermore, sialylation status has been shown to change during human adult life, impacting brain and muscle structural properties. Cardiac arrhythmias increase in prevalence with age, contributing to higher morbidity and mortality in the elderly. We aimed to investigate the impact of age-related changes in sialylation on Nav1.5 channels in cardiac cells. The Nav1.5 protein and sialic acid (α-2,3 and α-2,6) levels were quantified using SNA and MAA lectins in heart tissue from an aging mouse model. To investigate the role of sialic acid on Nav1.5 channel regulation, in vitro studies were conducted on HEK293 cells expressing Nav1.5 channels and induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Treatment with a mix of sialidase enzymes was performed for monitoring Nav1.5 protein biosynthesis, trafficking, degradation, and recycling and patch clamp analysis was used to examine changes in sodium ion current. To investigate the impact of exogenous sialic acid production on Nav1.5 protein expression, cells were fed with modified mannosamine. Our results revealed a reduction in both α-2,3 and α-2,6 sialic acid levels in aged mice, which positively correlated with Nav1.5 protein levels. In vitro experiments demonstrated that decreased external sialic acid upon treatment induced Nav1.5 channel internalization and activated endocytic pathways, leading to proteasome-mediated degradation. Conversely, exogenous sialic acid restored Nav1.5 protein levels on the cell membrane. In conclusion, our findings suggest that age-related reductions in sialylation status in cardiac tissue induce Nav1.5 channel internalization. Modulating sialic acid levels could potentially serve as a promising therapeutic strategy to prevent cardiac dysfunction in the elderly population.